SD12 has selective food preferences. She isn't a "fan" of chicken but will eat it in pasta and sweet and sour chicken. Doesn't "like" steak but will eat the crap out of it if it's in front of her. Doesn't like veggies but eats them with no problem hidden in food. Doesn't like spicy but eats wasabi with sushi. 

Where is this new lactose intolerance coming from? Is DH just testing you now that you're home?

Things like tuna, peas, spinach, carrots, jello.... all perfect for some who is lactose-intolerant.

A restaurant or school will not remove these items because SD has imaginary lactose-intolerance. Your DH needs to teach her what she can and cannot eat. If she truly IS lactose-intolerant, push those items to the back or put them in brown paper bags.

I think there must be degrees of lactose intolerance.  My dad can eat cheese, chocolate and yogurt without a problem.  Milk and ice cream are a problem, although he often is willing to suffer the consequences for ice cream.  Now he buys the Breyers lactose free ice cream.

There is no way I would throw away good food, or even stop buying it for the others, because one kid is lactose intolerant. 

I hope your DH takes the skid with him, or leaves him with BM.  No way should you get stuck with him if your DH isn't even in town.

Have your husband be the one to prepare special meals for his son. Problem solved. 

I do not consider myself lactose intolerant. But I had a lot of issues with acute diarrhea after eating ice cream or drinking milk after my gallbladder removal 20 years ago.   It only happens occasionally now after drinking milk. But I’ve cut down drastically on my milk consumption. 

Simple solution - don’t consume food that makes you feel bad. - or just shut up if you do it on purpose. 

A true dairy allergy (life threatening) is a totally different problem. 

I am lactose intolerant, diagnosed by the consultant. There are grades of lactose intolerant. Luckily mine is not too high so i can eat any hard cheese and yoghurt as these products have already partially broken down the lactose. You can buy tablets that help break down lactose too. They are made from a natural product called lactASE. You take a couple before eating. 

I wouldnt buy specialist products (apart from lactose free milk which is not expensive in long life cartons) also chocolate soya milk is not very expensive.  On the other hand you could just get him ice lollies instead.

Is the problem more that the condition has not been officially diagnosed and that you feel it is just one of Bm's whims? I get that, its annoying when people decide these things and then expect you to run out and buy expensive replacements.

What symptons, if any, does he show of this intolerance? 

When we came to the US, we were shocked at how much milk families consumed here.  Hard cheeses generally have less lactose so I can have small amounts (of gruyere).  Let Daadddeeeee make special meals the way Chef did to his prescious. (they only eat junk food)

I didn't read that your DH was demanding you cook/serve 'special meals' for his oldest son. So not sure why I keep reading 'let your Dh prepare blah blah'. 

What he asked is the milk, chocolate milk and yogurt is out and replaced with lactose-free. That's not an outrageous request if his oldest actually has lactose issues. And you also state DH himself has some lactose issues= read your three youngest may have and/or develop issues too. 

I'm going to assume that all birth test were routinely ran when SS was born?  Not something to entirely laugh off. My youngest (just turned 18 a while back now) was born with galactosemia. Fortunately she does have some enzyme activity, and yes, she can have some of this or that, but very little to no of that or this. 

Please do not use the argument of 'why can SS have this but not that'. Instead I'd like you to do some simple research on what supposedly your SS has been diagnosed with aka in your SS's case, lactose intolerant. And as you have witnessed, he is not totally intolerant. So that means he needs to be careful and he needs to limit, avoid and monitor certain foods. 

Please remember the kid is six. And you have SS, what? EOWE? Two days a week? 50/50? How often is SS there that his need to drink lactose-free would really affect your other three? Again, the kid is six. Does little brother really have to have chocolate milk seven days a week? If SS isn't there 24/7, I would think little brothers could be having real chocolate full milk aplenty, but on the days/times SS isn't there. 

Sure, as some suggested 'just teach the kid what he can't eat' ... ok. I disagree it is 'ok' to serve a drink one can not have and expect that kid just to suck it up. What alternative is SS being offered to also partake in while little brothers are guzzling down chocolate milk , woofing down bowls of ice cream and having their yogurt? Please don;t tell me nothing. Or a glass of water. Remember this kid is six. 

Now on to what brought this subject up right now? Why not a year ago or three months ago? Surely neither BM or Dad woke up one day this week, figured out the kid is lactose intolerant. Surely having the kid in your home and feeding him isn't something new. 

So what brought Dad to decide his oldest son's ingestion of all things lactose must be observed this week?  This question is more out of curiosity than anything else. And being as your DH doesn't bother to remember he has any kids the majority of the time (unless he's terrorizing them)  I'm surprised at this most recent and sudden concern of his. Or did you happen to use the 'my tummy hurts, I'm sick' of SS as an justification as to why he had to take SS this weekend instead of you trying to keep SS home? 

Almond milk is delicious and healthier than cow's milk anyway.

The kid may have a touch of lactose intolerance.  But then again, when I was younger, I swore I was allergic to Mashed Potatoes at my summer camp.  Truth?  They texture just grossed me out...lol.  But, as others have pointed out, milk and yoghurt have higher amounts of it vs the other items.

Now, I would NOT throw out food if others in the family can eat it.  But, I might make small accomodations like buying sherbet or italian ices instead of ice cream before I knew he was coming or have a quart of lactose free milk as well as have some of the lactaid pills on hand. 

Back to the two weekends in a row.  You need to stop trying to convince your DH to take him with him on his work weekends.  You are approaching this from a position of weakness.  TELL him you are NOT watching his son on his custody time if he is out of town.  He has two choices.  1.  refuse visitation on weekends he is not available.  2.  Take him with him.  THAT IS IT.  THOSE ARE HIS ONLY TWO OPTIONS.  This is NOT a negotiation.  This is a statement and a choice he needs to make.  You don't care which it is... but if he tries to leave the boy with you he will find you driving kid back to mothers and if she is not there you will be driving him to his work site out of town and leaving him.

This is not a request so please stop "asking" him.  TELL him you are not watching HIS child if HE is NOT IN TOWN. 

The child may be lactose intolerant (needs to be properly diagnosed), but that doesnt mean the household food supply needs to be centred around what he can and cant eat. It is more important that the child needs to be taught that there are certain things he can and cant eat. Alternatives may be provided.

I would not agree to tossing out dairy products for my own children because one of them had adverse affects to dairy. Those products just becomes off limits to the intolerant one. End of story.

I buy food for my house. I am a vegetarian. Does not mean I dont buy meat or dont cook it. I just dont eat it or taste a dish containing meat that I have cooked for BS and SS. There is no need to impose my choices or restrictions on the rest of the house.

(Otherwise I dont see a reason for a "visiting" stepkid to stay with you when his Dad is not home.)  

with what someone else's child is eating, especially one who does not live in my home full time. When you cook for your kids, offer him some (obviously minus any milk or yogurt), if he wants it, fine, if he doesn't, fine. Your DH can worry about getting him his special foods. He has a father and mother. 

Oh my lord.

SD12 is lactose intolerant as is DH.  There's no reason to not buy regular stuff for others - DH and SD12 just won't use it. Except for ice cream - DH will regret it but he'll eat it.  SD12 won't touch anything with milk products.  HOWEVER we do buy Lactaid milk, it's more expensive, but everyone can use it.  And SD12 can eat it.

If they are truly lactose intolerant, and my sister is as well, then they will most likely naturally NOT eat the stuff.  The battles my mother and sister had over her eating cheese or drinking milk (forced to) were epic.